Scum buildup in grey water tank

The shower drain and kitchen sink drain empty into a 55gal barrel and then is dispersed through a drain line. The problem is that there is a heavy buildup of a solid to semi a solid white scum in the barrel which clogs the drain line.

My question is what would cause this? I am thinking that I need a grease trap on the kitchen sink but my wife claims she has a screen in the sink drain to catch solids and she never pours grease down the drain. She thinks that the soap products we use are doing this.

Any suggestions on what I should do?

A grease trap is a very good start anyway.
Some come with a basket you can lift out, get rid of the gunk, clean and put back, they are easier to work with.

G.W. Farnum wrote:She thinks that the soap products we use are doing this. ...
Any suggestions on what I should do?

I feel she is right that this problem is being caused by the soap products, though I am not sure how to advise you there.

Maybe looking at the soap product to find the ones causing the problem and switch to something else.

I know nothing about grease traps.  Would one catch the grease in dishwater?  Or Soap scum in the shower?

Could the scum be caused by hard water?  If so maybe a water softener would help with the problem.

You and your wife are both right.
Looks like it's a combination of oil/grease (includes fats that are building up on your skin which you shower off)  and anionic surfactants in your soap products.

This combination creates a perfect habitat for Microthrix parvicella a string bacteria that makes a lot of troubles in communal sewage facilities and there they control them using chemicals, which you obviously do not want.

I can honestly only tell you the root cause but not how to handle them other than scoop them off and feed them to your trees/plants, because that's how I do it if they getting too nasty.

I ordered the Oasis book but it hasn't come in yet so I tried something else I found on Google which I think will work.  I am feeding the kitchen sink and shower water into the top of a 55gal drum. The drum is filled about 4/5 full with pine bark mulch. The outlets are at the bottom of the barrel.

The plan is to route the filtered water to a section of the garden where I will have dug another mulch filled area. The system I was looking at had an upside down 5gal bucket with the bottom removed sunk into this area. Worms will be added to this section.

I also emailed Uncle Jim's Worm Farm to see if  the worms could survive in the 55gal drum with the unfiltered greywater.  This would speed up the break down of the solids in the greywater.

This is the reply that I got from the worm farm:

"Our worms cannot be submerged in water as they will drown.  They must be kept moist but not wet, in a soil base.  We would recommend that you look around for Tubifex worms for something like this."

I have seen worm processing incorporated into a system without drowning the worms. Grease trap first. Then a sieve above your surge tank water line with worms and their bedding. It would catch your solids and the worms would process them into castings, easily flushed along with the water that easily escapes the sieve into your surge tank.

I was trying not to have the hassle of a grease trap but I may have to add one. The idea you described is what I wanted. Would the grease be harmful to the worms?

After much thought I decided to add some worms to the barrel filled with pine bark mulch. My thought is that the grey water comes in the top of the barrel. The solids are stopped by the pine bark while the water drains through. The barrel is never filled with water so I think the worms should survive.

I added 30 red worms. These are not the high priced mulching worms but a canister of fishing worms that I bought locally. If it works that would be great. If not I haven't broken the bank.